Childhood bipolar disorders (BP) remain a remarkably understudied area in spite of voluminous literature comprising case reports, small studies, investigations with poorly defined populations, and increasing interest in offspring of parents with BP. To address this paucity of systematic data, we propose a five year, prospective, blindly rated study of the age- specific clinical manifestations and naturalistic course of 7-16 year old children and adolescents with BP disorders. Two contrast groups matched for age, gender, ethnicity, and SES are proposed. One contrast group will have subjects with a diagnosis of ADHD to control for specificity of the findings to BP as opposed to any psychiatric disorder. A second contrast group will be a community case control group to control for reliability of the research assessment procedures and to provide an age-specific normative control. Both the BP and ADHD groups will be enrolled utilizing consecutive case ascertainment from public and private in-patient and out-patient facilities in the St. louis area. The community case control sample will be ascertained by the "acquaintance method." A total of 270 subjects (90 BP, 90 ADHD, and 90 community case controls) will be entered. Entry will be completed during the first two years of study. Frequency of assessment will be every six months for the BP group to optimize the identification of complex cycling patterns. The two contrast groups will be assessed at baseline and two years after baseline. Assessments will be multi-informant (parents, child/adolescent, teachers); multimodal (respondent based interview, self administered); and multi- domain (psychopathological, psychosocial, academic, cognitive, developmental/maturational, temperament, family history). Findings of the proposed work will fulfill the practitioner's need for diagnostic and prognostic information that can be used to educate families an aid in therapeutic interventions (e.g. knowledge of time course can help determine length and aggressivity of therapy). For investigators, the findings will provide a framework for more focused neurobiological, familial-genetic, and treatment studies. The high rates of suicide an substance dependency in adolescent BP warrant intense efforts to increase our knowledge of childhood onset BP disorders.